Flagged brush bristles



March 16, 1965 F. R. CRAMTON FLAGGED BRUSH BRIS'I'LES Filed March 29, 1963 N 5 Km H. mm m WM 0 M6 A United States Patent 3,173,163 FLAGGED BRUSH BRISTLE Frank R. Cramton, Burlington, Vt., assignor to E. B. & A. C. Whiting Company Filed Mar. 29, 1963, Ser. No. 269,078 3 Claims. ,(Cl. 15-159) This invention relates to novel synthetic resin filaments for use as bristles in brushes. More particularly, this invention relates to flagged brush bristles comprising polypropylene and to a brush made from such bristles.

It is well known that the most widely used brush bristles to date have been made of animal hair. Due to the difiiculty and expense required to obtain and manufacture such bristles, the industry has turned to the use of bristles made from a variety of synthetic fiber compositions. Originally, nylon and polystyrene bristles were used but such bristles were not highly successful because they lack retention and have a tendency to scratch polished surfaces. In order to overcome such deficiences, the bristle industry has developed a process known as flagging whereby the ends of the bristles or filaments are split into many longitudinal slivers or fibers. As a result of the development of the fiagging process, it is possible to make synthetic bristles which have good body, retain as much liquid as do natural bristles and which do not scratch polished surfaces. However, it has been found that very few bristles made from synthetic resin compositions may be flagged with any degree of success. For example, nylon bristles were one of the first synthetic resin bristles to be flagged successfully. However, they were not completely satisfactory because the degree of flagging was low. More recently, in order to obtain increased flagability, flagged bristles composed of two or more incompatible synthetic resins have been developed. For instance, bristles comprised of a mixture of nylon and polystyrene have been successfully flagged. However, even these bristles possess certain disadvantages. For example, nylon absorbs substantial amounts of water thus resulting in a flexible limp bristle. Moreover, the abrasion resistance of these bristles has not always been satisfactory. Abrasion resistance and stiffness are of prime importance when making bristles primarily designed for heavy duty jobs such as in street brushes.

The foregoing described disadvantages are avoided by the practice of this invention, which briefly, comprises producing a longitudinally oriented filament or bristle consisting essentially of from about 5% to about 95% by weight of a polyolefin such as polyethylene or polypropylene, the remainder being substantially an incompatible synthetic resin selected from the group consisting of polystyrene and styrene-acrylonitrile copolymers. The polyolefin is preferably isotactic polypropylene. The flagged filament or bristle is produced by preparing a mixture of from about 5% to about 95% polyolefin, the remainder being either polystyrene or a copolymer of styrene and acrylonitrile, introducing the mixture into a heating zone, melt extruding a filament from the mixture, quenching, subsequently heat softening the filament and longitudinally stretch orienting the filament. The quenching bath may be either hot or cold depending upon which constitutient is used in major proportions. A cold quenching bath is generally used when the major constituent is polypropylene.

After the filament has been softened, it is stretched longitudinally to increase the molecular orientation along the filament axis. Any amount of stretching will increase the molecular orientation. However, maximum benefits are obtained by stretching the filaments from about 6 to about 11 or more times the length thereof.

The preferred polyolefin which may be used in the practice of this invention is isotactic polypropylene which is a high molecular weight (i.e., above about 45,000) solid polymer exhibiting a crystalline X-ray difiraction pattern. Such a polymer has a density between 0.90 and 0.94 and a melting point above about 320 F. These polymers may be prepared by methods now well known in the art such as by the procedures described by G. Natta in the Journal of Polymer Science, vol. XVI, pp. 143 to 154 (1955) and in US. Patents 2,882,263; 2,874,153 and 2,913,442.

The polystyrene and styrene-acrylonitrilecopolymer which may be used in the practice of this invention may be any high molecular Weight (i.e. above about 45,000) polymer. The copolymer preferably should contain from about 20% to about 40% acrylonitrile.

The filaments or bristles produced according to this invention are extremely useful in the production of tufts of bristles which are readily mounted in brush heads for use as paint brushes, scrub brushes, broom, street brushes, etc. Brushes produced according to the practice of this invention are more resistant to abrasion and moisture than are any of the prior art bristles. They are also resistant to various organic solvents which may deleteriously affect bristles containing a polyamide.

The aspects of this invention which are capable of illustration, are shown in the accompanying drawings.

FIG. 1 is a schematic view of a suitable overall arrangement of apparatus for producing the filaments according'to this invention.

FIG. 2 is a side view of a flagged bristle made according to the present invention.

FIG. 3 is a view of a section of a brush in which the bristles of this invention are adapted fo use.

In FIG. 1, a hopper 10 contains a homogeneous mix ture 11 of polyolefin pellets such as isotactic polypropylene and a styrene-acrylonitrile copolymer in predetermined proportions. The mixture 11 may be preheated in the hopper 10 if desired. From the hopper 10 the mixture is conveyed by means of a heated extrusion chamber 12 to a heated extrusion head 13 which contains an extrusion die 13a. In the extrusion chamber 12, the tem perature of the mixture is raised to above the melting point of the mixture. It is extruded through suitably shaped orifices in the extrusion die 13a into one or more filaments 14. A preferred extrusion temperature for a mixture of isotactic polypropylene and polystyrene is about 480 F. The filaments 14 are extruded at a linear rate of from about 18 to about 50 feet per minute from the orifices, the size of which may range from about 10 mils to about 250 mils in diameter.

In making filaments in which isotactic polypropylene is the major constituent, it is advantageous to quench the extruded filaments in order to solidfy them. This may be accomplished, as shown in FIG. 1, by placing a quenched bath 15 between the extrusion head 13 and the heating chamber 22. The extruded filaments 14 are guided into the quench bath 15, containing a liquid nonsolvent, e.g., water, by a guide roll 16. The bath 15 is maintained in a suitable tank 17 at a temperature of 60 F. or below. Temperatures of about 40 F. are preferred. However, when either the polystyrene or the styreneacrylonitrile copolymer constitutes the major constituent, a quench bath temperature in excess of F. should be maintained. An immersion time of from about 8 seconds to about 20 seconds in the bath 15 is generally sufficient. The filaments 14 are transported around a stationary pin 18 in the quench bath 15 and then over the roll 19 and into the hot air conditioning oven 22. In the oven, the extruded filaments are transported over a number of rolls 2 0, which may be heated, in a sinuous or zig-zag path, as heated air is circulated from overhead. As the filaments pass through the heating zone, each succeeding driven roll 20 over which the filaments 14 pass is driven at a slightly increased peripheral speed from that of the preceding roll so as to prevent the filaments from sagging appreciably. The primary purpose of the series of driven rolls is to provide a heat exchange relationship between the filaments 14 and the heated air in the oven whereby the filaments are uniformly softened by heat.

After leaving the last and uppermost driven roll 20, the filaments are snubbed with a three roll assembly 21, each roll of which is driven at about the same as or a higher peripheral Speed than that of the last driven roll 20. A fast snub roll assembly 23 is provided just outside the oven 22 which is driven at a peripheral speed of about 6 to 11 times that of the assembly rolls 21. Thereby, the filaments 14 are stretched from about 6 to 11 times their length. Stretching increases the molecular orientation along the fiber axis. The drawn, oriented filaments 14 are thereafter collected on reel 24 which is supported on frame 25. Thereafter, the wound filaments may be cut in appropriate lengths and flagged. Alternatively, the reels may be shipped to the brush manufacturer and subsequently flagged by the manufacturer either before or after the brush if formed.

Any suitable means may be used to fiag the ends of the filaments. For instance, tufts of filaments may be mounted in a brush head and held against a propeller-like blade which is rotated in such a manner as to abuse the filament ends.

In FIG. 2 the bristle 14 as shown has been flagged at one end by conventional flagging means such as those described above. Each bristle 14 is split into many longitudinal sub-filaments or bristles 27, which in turn are split into progressively finer sub-filaments v28. The bristles 14 are then grouped together into tufts and inserted into retaining means (i.e. holes, clamps, etc.) 31- on a rotary street brush base 32 as shown in FIG. 3. The

tuft ends appear as fine subfilaments 28.

The following examples illustrate the best mode contemplated for carrying out this invention.

Example 1 Eighty (80) parts by weight of isotactic polypropylene pellets having an average molecular weight of about 100,000, a density of 0.90 and a crystalline melting point of 332 F. is admixed with 20 parts by weight of a copolymer of acrylonitrile and 65% styrene. The mixture is fed into a screw extruder of the type shown in FIG. 1 having a 2.5 inch screw diameter. The die plate contains 3 extrusion orifices, each having a circular shape. The heating jacket is heated to a temperature of about 480 F. and the bristles are extruded at a linear rate of 35 feet per minute from the orifices. The filaments are then passed through a quench bath maintained at a temperature of about 60 F. to solidify them. They are then fed into a heating chamber and heated to a temperature of about 300 F. before they leave the chamber. After leaving the heating chamber, the filaments are stretched to about 7 times their original length.

4- The longitudinally oriented bristles are wound on reels.

Example 2 Eighty parts by weight of isotactic polypropylene pellets are admixed with 20 parts by weight of polystyrene pellets, each having a molecular weight of above 45,000, and processed according to the procedure described in Example 1. The flagged bristles thus formed possess improved resistance to abrasion and moisture.

Example 3 Eighty (80) parts by weight of polystyrene pellets are admixed with 20 parts by weight of isotactic polypropylene pellets and processed according to the procedures described in Example 1. However, the quench bath temperature is maintained at 130 F. The flagged bristles produced accordingly possess good abrasion resistance.

Example 4 Twenty (20) parts by weight of isotactic polypropylene pellets are admixed with 80 parts by weight of styreneacrylonitrile copolymer pellets and processed according to the procedures described in Example 1, except that the temperature of the quench is maintained at 120 F. The flagged bristle produced accordingly possess good abrasion resistance.

I claim:

1. A longitudinally oriented flagged brush bristle consisting essentially of a mixture of from about 5% to about 95% by Weight of isotactic polypropylene, the remainder being substantially an incompatible synthetic resin selected from the group consisting of polystyrene and styrene-acrylonitr-ile copolymers.

2. A longitudinally oriented flagged brush bristle as set forth in claim 1, wherein said bristle consists essentially of from about 70% to about by weight of said isotactic poly-propylene.

3. A brush containing the flagged bristles as set forth in claim 2.

References Cited by the Examiner UNITED STATES PATENTS 2,282,002 5/42 Scott et a1 260-45.5 2,812,530 11/57 Whitesel 15-159 2,945,827 7/60 Henning 260-455 2,957,847 10/60 Salyer 260-45.5 3,017,238 1/62 Levine et al. 264176 X 3,050,821 8/62 Kilian 161-173 3,059,991 10/62 Munt l5159.1 3,065,190 11/6 2 Chisholm et a1 260-455 3,118,161 1/64 Crarnton 15-159 3,121,040 10/64 Shaw et a1. 161177 FOREIGN PATENTS 853,802 11/60 Great Britain. 885,926 1/62 Great Britain.

CHARLES A. WILLMUTH, Primary Examiner. 

1. A LONGITUDINALLY ORIENTED FLAGGED BRUSH BRISTLE CONSISTING ESSENTIALLY OF A MIXTURE OF FROM ABOUT 5% TO ABOUT 95% BY WEIGHT OF ISOTACTIC POLYPROPYLENE, THE REMAINDER BEING SUBSTANTIALLY AN INCOMPATIBLE SYNTHETIC RESIN SELECTED FROM THE GROUP CONSISTING OF POLYSTYRENE AND STYRENE-ACRYLONITRILE COPOLYMERS. 